Titanium oxide (represented by TiO2(B)) having a monoclinic β-type structure has recently attracted much attention as an active material for a non-aqueous electrolyte battery. Spinel type lithium titanate (Li4Ti5O12), which is currently in practical use, is limited to 3 in the number of lithium ions which can be inserted and desorbed per unit chemical formula. For this reason, the number of lithium ions which can be inserted and desorbed per titanium ion is ⅗ (0.6) which is a theoretical maximum. In the case of TiO2 (B), on the other hand, the number of lithium ions which can be inserted and desorbed per titanium ion is 1.0 at maximum. Therefore, TiO2 (B) has a theoretical capacity as high as about 335 mAh/g.
However, the practical electrode capacity of TiO2 (B) is about 170 to 200 mAh/g, which is significantly lower than the theoretical capacity. This is because, though there are many sites which can serve as Li hosts in a crystal structure of TiO2 (B), mobile Li ions are reduced because the diffusibility of Li ions in a solid is low, and also, Li ions are trapped by impurity phases and crystal grain boundaries. Accordingly, the initial irreversible capacity is large, and therefore a high capacity cannot be obtained.